Donald Trump, Xi Jinping

Andy Wong / AP

FILE - In this Nov. 9, 2017 file photo, U.S. President Donald Trump, right, chats with Chinese President Xi Jinping during a welcome ceremony at the Great Hall of the People in Beijing. President Trump is offering to mediate in the South China Sea disputes, while his Chinese counterpart Xi Jinping is playing down Chinaâs military buildup in the disputed waters. Itâs not clear how serious Trumpâs offer is and China is likely to reject any expanded U.S. role. Philippine President Rodrigo Duterte said Xi, during a meeting in Vietnam, where they attended the annual Asia-Pacific Economic Cooperation forum, assured him of China's peaceful intentions in the strategic waterway. (AP Photo/Andy Wong, File)

FILE - In this Nov. 9, 2017 file photo, U.S. President Donald Trump, right, chats with Chinese President Xi Jinping during a welcome ceremony at the Great Hall of the People in Beijing. President Trump is offering to mediate in the South China Sea disputes, while his Chinese counterpart Xi Jinping is playing down Chinaâs military buildup in the disputed waters. Itâs not clear how serious Trumpâs offer is and China is likely to reject any expanded U.S. role. Philippine President Rodrigo Duterte said Xi, during a meeting in Vietnam, where they attended the annual Asia-Pacific Economic Cooperation forum, assured him of China's peaceful intentions in the strategic waterway. (AP Photo/Andy Wong, File) (Andy Wong / AP)

FILE - In this Nov. 9, 2017 file photo, U.S. President Donald Trump, right, chats with Chinese President Xi Jinping during a welcome ceremony at the Great Hall of the People in Beijing. President Trump is offering to mediate in the South China Sea disputes, while his Chinese counterpart Xi Jinping is playing down Chinaâs military buildup in the disputed waters. Itâs not clear how serious Trumpâs offer is and China is likely to reject any expanded U.S. role. Philippine President Rodrigo Duterte said Xi, during a meeting in Vietnam, where they attended the annual Asia-Pacific Economic Cooperation forum, assured him of China's peaceful intentions in the strategic waterway. (AP Photo/Andy Wong, File)